Production of gray cast iron



July 29. 1924. 1,502,983

' P. A. DIEFENTHALER I PRODUCTION OF GRAY CAST IRON Filed April 2, 1921 I N VENTOR ATTORNEY latented July 29, 1924. i

UNITED. STATES v I 1,502,983 PATENT- OFFICE.

mn'mrr nuousr DIEF NTHALER. or HEIDELBERG,- GERMANY, ASSIGNOR TO ran 7 rum nnnmrcn LANZ, or mmmmm, mama, GERMANY, A cornarnaasmr.

PRODUCTION OF GRAY CAST IRON.

Application am April 2, 1921. Serial No. 458,049.

1 e'nmai man HIE rnovrsmns or rm: ACT or MARCH 3, 1921, 41 STAT. I.., 1313.)

. T all whom it may concern:

B'e it known that I, PHILIPP AUGUST Dmrnu'rnlinnn, residing at 5* Rombachweg, Heidelberg, Baden, Germany, have invented if certain new and useful Improvements in and Relating, to the Production of Gray Cast Iron .(for which I filed applications in Germany, 1132,571, May 9, o 1916, Pat. No. 301,913 Austria, A6118/18, Nov. 23, 1918, Pat. No. 80,884; Hungary, D3,121, Nov. 6,

1918, Pat. No. 75,662), of which the followin is a specification. n the use of cast iron for machine parts, which'are subjected to much friction, such as bearings, steam cylinders, slide blocks, pistons, guides, and the like, for a long time, conflicting and: very often unsatisfactory results have been experienced. Whilst in some cases, such articles last well in use for 1 manyyears, other machine parts of the same kind soon wear awayand, by running hot and col'roding, often lead to diliicultiesv in operation. It has been attempted to overcome these drawbacks by producing the cast iron exactly on the basis of analytical experiments without, however, leading to uniform results. 4 I 'havediscovered that it is absolutely necessary to produce a definite texture or struc-- tural condition in such articles in order, in all circumstances, to exclude the difliculties referred to. i

The congealing diagram of cast iron shows, as is well known, two distinct conditions': on the one hand,-iron with combined carbon, and on the other hand iron with the carbon inv the form of graphite. Between these two limiting'conditions-cementite on the one side'and ferrite on the other side- 4 the transitional condition ofpearlite is formed. I have found that a well-developed, uniformly distributed, lamellar pearlite structure, with moderate. graphite veining, no free ferrite being formed, gives the casting, besides great strength, the capacity of withstanding frictional wear to a very great degree.

Such astructure is-illustrated in the accompanying drawing, wherein is shown a microphotograph of a somewhat large complex, magnified'250 times, composed of several granules of banded pearlite with only interspersed veinings a of graphite.

'The thickness of the casting, and other factors on which the cooling rate depends, must be taken into account and in order to obtain with certainty the lamellar pearlite structure, excluding free ferrite, desired, the cooling should be effected as gradually as possible.

The solution of the problem, therefore, consists in first choosing such a composition of low carbon and silicon content as to allow the forming oflpearlite and graphite and finding out empirically, for a definite composition and the different cross-sections of the casting, the heat curve according to which with certainty the desired pearlite structure is obtained and then cooling the finished casting in the mould according to this'teinperature curve. This can be done, for example, satisfactorily by bringing the mould preliminarily to a definite temperature. It has been found, for example, in the case of a composition of 3 per cent carbon (of which 0.85 per cent is combined with the iron and thus forms pearlite and the remaining 2.15- per cent occurs as finely dis: tributed graphite), 1 per cent silicon, 0.7 per cent manganese, 0.4 per cent phosphorus, 0.1 per cent sulphur and 94.8 per cent iron that the mould hould be preliminarilyheated to the following temperatures For a thickness of material of about 10 millimeters to about 390 F.

For a thickness of material of about 20 106" millimeters to about- 300 F.

For a thickness of material of about 30 ly distributed graphite) and 0.8 per cent silicon, the preliminary temperature-of the mould should be selected about 70 to 80 F. higher, that is to say For a thickness of 10 millimetres about 470 F.

For a thickness of 20 millimetres about 380 F.

For a thickness of 30 millimetres about 290 F.

It may be seen from these examples, that it is a comparatively simple matter to prepare scales or curves fora particular composition from which, without further trouble, the necessary temperature of the mould can be read for a particular thickness of material.

Alternative methods of carrying out the process to produce the lamellar pearlite structure consist in heating the molten iron to a higher temperature such that the excess of heat serves for the necessary heating of the mould or by inserting the mould after casting in a heated chamber the tem perature of which can be easily regulated so as to cool the casting according to the empirically obtained cooling conditions.

For preheating the mould a heated chamber may be employed through which the mould is drawn by means of a transporter band or similar means, the duration of travel and temperature of chamber being such that the mould acquires the requisite temperature. The same chamber can be used for the latter of the two alternative methods mentioned. Accordingly the metal is cast in a cold mould and the mould is brought into the heated chamber as quickly as possible and left therein for a sufficient time to permit the pearlite structure to develop. In this case also empirical curves can be readily plotted from which according to the composition, the thickness of the casting and the temperature prevailing in the chamber the requisite duration of the passage of the mould through the chamber can be read off. When the mould is taken out of the chamber it is allowed to cool in the ordinary way.

According to these technical rules,'it is possible"-to produce gray cast iron which will stand frictional wear to a very high degree.

What I claim as new, and desire to secure by Letters Patent, is-

1. The method of producing gray cast iron having a uniformly distributed lamellar pearlite structure with moderate veinings of graphite and with little if any free ferrite which consists in making the castings from an iron composition with a low content of carbon and silicon and in heating the mould to a temperature above normal to artificially retard the cooling of the castings therein and permit the pearlite structure to develo 2. The-method of producing gray cast iron of predominantly lamellar pearlite structure and of high resistivity to frictional wear which consists in using for the castings an iron composition having a low content of carbon, silicon, manganese, phosphorous and sulphur and in retarding the cooling of the castings in the mould according to temperature curves, based upon the heating of the mould to a temperature varying according to the particular composition and the thickness of the casting, adapted to limit the formation both of free ferrite and of cementite.

3. The method of producing gray cast iron of predominantly lamellar pearlite structure which comprises starting with an iron composition having a low content of carbon and of silicon and retarding the cooling of the castings, as by cooling them in moulds heated above normal to a temperature dependent uponi the particular composition used and the thickness of the castings, to the extent required for the development of the pearlite structure. I

4. Gray cast iron of great strength and highly resistant to frictional wear which structure with moderate graphite veinings and with little if any free ferrite.

In testimony whereof I have afiixed my signature in presence of two witnesses.

I PHILIP? AUGUST DIEFENTHALER. Witnesses:

MAX STRAUSS, Emo LEHMANN. 

